Nipple-electrode assembly

ABSTRACT

The invention relates to nipple-electrode assemblies and joints, such as those used in electric arc furnaces, and to a means of distributing thread clearance throughout the assembly and/or joint. These means include the pre-positioning of the nipple in the socket of the electrode section into which the nipple is threaded so as to provide a clearance between the non-load bearing flanks of the threads of said threaded nipple and said threaded electrode socket and the placing within the space between the base of the nipple and the bottom of the socket of the electrode section a hot, non-gaseous fluid, carbonizable material which solidifies upon cooling, thereby preparing a preassembly wherein the nipple is fixed in the electrode section, thereby maintaining the aforedescribed pre-positioning and thread clearance and thereby also providing room for thermal expansion of the threads of the connection. The hot, carbonizable material is introduced into the space between the base of the nipple and the bottom of the socket, while in a hot, fluid condition, through a hole in the nipple after the nipple has been threaded into the electrode socket, after which the carbonizable material solidifies. Upon connection of the projecting end of the nipple into a socket of an electrode section and use in a column of electrodes in an electric arc furnace, the solidified carbonizable material again becomes heated, melts and some of it flows downwardly through the hole into the corresponding space in the socket of the electrode section of the column and then becomes solid and carbonizes due to the heat encountered, thereby locking the nipple in the sockets of both electrode sections joined.

I United 9 States Patent [191 Gazda 1 ,lune4,1974

[ 1 NIPPLE-ELECTRODE ASSEMBLY [75] Inventor: Irving William Gazda, Johnson City,

' Tenn.

[73] Assignee: Great Lakes Carbon Corporation, New York, NY.

[62] Division of Ser. No. 113,995, Feb. 9, 1971, Pat. No.

52 us. (:1. 13/18 [51] Int. Cl. 1105b 7/14 [58] Field of Search 13/18; 287/127 E 56] I I References Cited I UNITED STATES PATENTS 2.510.231) 6/1950 Johnson 287/127 E 2,828.162 3/1958 Johnson 287/127 E 2,894,776 7/1959 Johnson 287/127 E 2,941,828 6/1960 Hund et al. 287/127 E 3,140.967 7/1964 Kaufmann et a1... 287/127 E- X 3.517.954 6/1970 Snyder et al 13/18 X Primary E.ruminer.-Roy N. Envall, Jr. Attorney, Agent, or FirmWallace F. Neyerlin and to a means of distributing thread clearance throughout the assembly and/or joint. These means include the pre-positioning of the nipple in the socket of the electrode section into which the nipple is threaded so as to provide a clearance between the non-load bearing flanks of the threads of said threaded nipple and said threaded electrode socket and the placing within the space between the base of the nipple and the bottom of the socket of the electrode section a hot, non-gaseous fluid, carbonizable material which solidifies upon cooling, thereby preparing a preassembly wherein the nipple is fixed in the electrode section, thereby maintaining the aforedescribed prepositioning and thread clearance and thereby also providing room for thermal expansion of the threads of the connection. The hot, carbonizable material is introduced into the space between the base of the nipple and the bottom of the socket, while in a hot, fluid condition, through a hole in the nipple after the nipple has been threaded ,into the electrode socket, after which the carbonizable material solidifies. Upon connection of the projecting end of the nipple into a socket of an electrode section and use in a column of electrodes in an electric arc furnace, the solidified carbonizable material again becomes heated, melts and some of it flows downwardly through the hole into the corresponding space in the-socket of theelectrode section of the column and then becomes solid and carbonizes due to the heat encountered, thereby locking the nipple in the sockets'of both electrode sections joined.

4 Claims, 8 Drawing Figures PATENTEUJun 4 I974 SHEET 1 [IF 4 FIG. I

PATENT EDJUH 4 I974 SHEET 2 BF 4 PATENIEBM 4 m SHEET t [If 4 1 NIPPLE-ELECTRODE ASSEMBLY This application is a Divisional Application of application Ser. No. 113,995 filed Feb. 9, 1971 (now US. Pat. No. 3,717,911, issue date Feb. 27, 1973).

BACKGROUND OF THE lNVENT-ION '1. Field of the Invention This invention relates to the field of graphite electrodes such as those used in electric arc furnaces and like equipment, wherein the'electrodes are consumed in use and wherein the electrodes must be continually fed into the furnace or other equipment where they are used. In order to facilitate this continual feed, the electrode sections are suitably bored and threaded at each end to provide juncture means through a correspondingly shaped and threaded nipple. In this manner, a new electrode is joined to the one being'consumed by inserting a nipple into the bore of either the new or partially consumed electrode section vand joining the: composite electrode section-nipple assembly to the other electrode section. Such nipples and their corresponding bore holes in the electrode sections may have threaded sides which are parallel to the nipple axis. it is generally more customary and advantageous, however, to taper the nipple so that its largestdiameter is at its middle and is also at the plane of contact between the electrode sections. Such a tapered nipple is screwed into place in a correspondingly tapered threaded bore or socket of the electrode section with the small diameter end or nipple base going furthest into the electrode body. In threading the taperednipples for use injoining electrode sections, the thread depth is generally the same, whether measured at the small diameter ends or bases or at the large diameter center. It isalso usual that in the assembled joint each thread will possess a loaded flank, which is nearer the geometric center of the nipple, and a non-load bearing or idle flank which is opposite to the loaded flank. (That is, the idle flank is the flank nearer the ends of the nipple and the loaded flank is the flank nearer the geometric center of the nipple, and this is how these flanks are defined in the present invention). The loaded flank generally carries most, if not all, of the compressive-stress between the nipple and the electrode sections.

In this type of. joint, the half that is assembled first usually contains little or no clearance at the idle flank V tween the threads of the nipple and the electrode sockets and consequent reduction in thermal stresses be tween a nipple and the electrode sections into which it is threaded, and also relates to making the connections between the electrode sections and connecting nipples tighter and less able to become unwound, and offers a novel and advantageous approach for simultaneously accomplishing each of these conditions or objectives.

SUMMARYOF THE INVENTION It is an object of the present invention to provide a nipple-electrode section assembly or pre-assembly in which there is a more evenly distributed clearance (as compared to conventional commercial practices) between the idle or non-load bearing flanks of the threads of the nipple and the threads of the electrode section socket, so as to provide room for thermal expansion of said threads.

- It is another object of this invention to substantially evenly distribute thread clearance throughout a nippleelectrode section pre-assembly, and also throughout an entire electrode joint assembly comprising two elec-' trode sections having threaded sockets in the ends thereof and a nipple threaded into said sockets, joining the electrode sections together. It is another object of this invention to accomplish the aforesaid more even distribution of thread clearance in an advantageous and practical manner while simultaneously making the conwhile maximum clearance occurs at the idle flank of the second half assembled.

in such joints it also has not been unusual for the electrode sections to loosen and to become unwound from around the connecting nipples thereby frequently causing high power and/or graphit material losses due to increased electrical resistances at the joints and/or an electrode section becoming completely unthreaded and falling into .the metal bath at the bottom of the furnace. r

2. Description of the Prior Art There has been a well recognized need to more evenly distribute the aforedescribed'clearance differences in order to reduce or counteract thermal stresses which build up due to lack of expansion room and result in cracking the joint, and various methods have been proposed by those skilled in the art to accomplish substantially even distribution of thread clearance. For example, thisproblem and several proposed solutions nections between the electrode sections and connecting nipple tighter and less able to become unwound and in a manner which is also novel as compared to techniques which have been suggested or taught by the prior art for solving these problems.

The invention, in a preferred embodiment, comprises the making of an improved nipple-electrode section 501 pre-assembly, such as described, by:

a. Providing a hole starting at a point in an end face of one-half of the nipple and terminating at a point in the surface of the other half of the nipple;

b. pre-positioning the nipple in the socket of the electrode section by threading an end thereof possessing a hole in its end face, into the internally threaded socket so as to provide a space between the base of the nipple and the bottom of the electrode section socket and a clearance between. the non-load bearing flanks of the threads of said threaded nipple and the opposing faces of the threads of the electrode socket, said non-load bearing flanks of the threads being those nearer to the ends than to the geometric center of the nipple;

c. introducing a hot, non-gaseous fluid, carbonizable material through the exposed end of the hole of the nipple in sufficient quantity so that immediately upon in troduction it at least substantially fills the space between the base of the nipple and the bottom of the socket of the electrode section without undergoing any subsequent expansion; and

d. permitting said hot fluid material to become substantially solid by cooling it to ambient temperature, thereby fixing the nipple in the electrode section and thereby also maintaining the pre-positioning and thread clearance of (b) and providing room for thermal expansion of the threads of the connection.

Preferably the pre-positioning of the nipple in step b is effected by utilizing a temporary positioning means, such as is described hereinafter, which temporary positioning means is removed after the hot fluid material has been cooled and become substantially solid, as in step d.

Other objects, and coincident advantages, and a complete understanding of the invention will be apparent to those skilled in the art after a study of the drawings, and a reading of the secification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS It has been found thatthe foregoing objects are achievable by making-a nipple-electrode section preassembly such as illustrated in vertical cross-section in FIG. I and by using such a pre-assembly as a part of each joint assembly used in the electrode'column. FIG. 2 illustrates auxiliary equipment, viz. a centering jig, which may be used as a temporary positioning means in carrying out the processes of or in making the'preassemblies of the present invention.

FIG. 3 illustrates in FIGS. 3a, 3b, 3c and 3d embodiments of four alternate hole orientations or arrangements in the nipple that may be employed in the present invention besides the use simply of a central hole as illustrated in FIGS. 1 and 2. The nipple must always possess at least one hole extending in an axial or generally lengthwise'direction (c.f. FIG. 1), but, as is apparent from FIG. 3d, one or more additional holes may also sometimes be employed in conjunction therewith. (This is discussed in more detail hereinafter). The axial or generally lengthwise hole must always start at a point in an end face of one-half of the nipple and terminate at a point in the surface at the other half of the nipple. Preferably the lengthwise hole will extend from one end face of the nipple tothe other end face, as illustrated in' FIGS. '1, 3a, Sb-and 3d. Less preferably it may also terminate at a point in the surface of the other half of the nipple which is not in the opposite end face of the nipple. FIG. 30 illustrates this possible embodiment of the invention. FIGS. 4 and 5 illustrate the final assembledjoints described in the present invention, (employing the pre-assembly illustrated in FIGS. 1 and 2 FIG. 4 illustrating the condition of the joint when first assembled and FIG. 5 illustrating the condition of the joint thereafter after there has been melting and downward flowing of some of the carbonizable material from the space between the base of the nipple and the bottom of the socket of the electrode section of the pre-assembly.

DETAILED DESCRIPTION OF THE DRAWINGS AND OF THE PREFERRED EMBODIMENTS As illustrated in FIG. I, the nipple l, which as previously stated is preferably tapered, was threaded into a correspondingly tapered and threaded socket of electrode section 2. The nipple was provided with a central, axial or longitudinal hole 8 which'extended lengthwise from one end face'6 of the nipple to theother end face 9. The nipple had a major diameter of 10 inches, the

diameter of the longitudinal hole was I A; inches, and the diameter of the electrode section 2 was inches. The nipple also had a one-third pitch, i.e. three threads per inch, and a taper of l to 6, i.e. its radius decreased by one inch for every six inches of length of the nipple away from the maximum diameter. The nipple was threaded into the socket until its major diameter, indicated generally at 3, coincided approximately with the plane of the face 4 of the electrode section and until it was hand-tight," i.e. until the threads of both the nipple and electrode socket section were completely engaged. The nipple was then pre-positioned in the electrode section socket by being backed-off a slight amount such as an eighth tum (i.e. 45) so as to provide a clearance between the idle flanks of the threads of said threaded nipple and said threaded electrode socket. A centering jig temporary positioning means was employed during the pre-positioning of the nipple. (More is stated regarding this in connection with FIG. 2). r A hot, non-gaseous fluid, essentially non expandable, carbonizable material was then introduced or forced' through the hole 8 in sufficient quantity so that immediately upon introduction it at least substantially filled the space 5 between the base 6 of the nipple and the bottom 7 of the electrode section socket, without undergoing any subsequent expansion. (More will be said regarding such fluid, carbonizable materials and their nature or composition hereinafter). An excess of the hot, fluid, carbonizable material was employed (and this is typical)and this extended partially up the lengthwise or longitudinal hole such as to level 10, which is typically at least midway up the hole 8 and more preferably to a level such as will substantially fill the hole 8 as well as the space 5. As the material cooled to ambient temperature-it solidified and substantially or completely filled any void area in the space 5 and also served to fix the nipple in the desired position in the electrode socket. The solidification of the material also maintained the aforediscussed pre-positioning and thread clearance of the nipple, thereby also providing room for thermal expansion of the threads of the connection, The pre-positioning of the nipple also caused the upper faces or load-bearing flanks ll (viz. the

, flanks nearer the geometric center of the nipple) to contact the mating faces of the threads of the socket and also caused or created a slight gap or clearance 12 at the idle or non-load bearing flanks or sides 13 of the thread, viz. the flanks nearer the end 6 of the nipple. (It is clear from the foregoing discussion, of course, that the pre-assembly and the positioning of the members thereof is effected prior to the additionof the preassembly to an electrode column on a furnace).

Drilling the hole 8 off-center may also be restored to and typical ways that this might be done are illustrated in FIG. 3, embodiments 3a, 3b and 30. In FIG. 3a the axis of the hole is parallel with the axis of the nipple. In FIG. 3b the hole extends lengthwise from one end face of the nipple to the other end face but the hole is at an angle to the nipple axis. In FIG. 30 the hole starts at a point in an end face of one-half of the nipple and terminates at a point in the surface of the other half of the nipple (as do also the holes of FIGS. 1, 3a and 3b) but does not fully extend to the other end face of the nipple. In other words it exits on the threaded lateral surface of the nipple. This is not as desirable as exiting from a position on the end face of the nipple but it does define an operable position for introducing the hot fluid material into the hole and'is within the scope of the present invention. Also, in this'embodiment, the point of exit of the hole on the threaded lateral surface is preferably nearer the end than the center of the nipple but is also typically a distance of at least about onesixth the length of the nipple from the end.

FIG. 3d illustrates the use of two lateral or generally transverse holes 8a and 8b which intersect or connect at an angle with the lengthwise hole 8. These holes are typically of smaller diameter than the lengthwise hole 8. FIGS. 3a, 3b, 3c and 3d also show the typical position of the carbonizable material within the clearance space 5 and the holes 8 (and 8a and 8b) of the preassembly before the exposed nipple end of the pre assembly is connected to another electrode section.

The invention is intended to cover pre-positioning of the nipple so as to cause a clearance between the idle flanks of the nipple and the threads of the socket of the electrode section no matter how the pre-positioning of the nipple is effected so long as the other steps of the invention arepractised. However, it is preferred that an auxiliary device or temporary positioning meanssuch as a centering jig" be used in order to provide optimum pre-positioning of the nipple.

(The backing-off" of 45 of the nipple in the embodiment just described is satisfactory for a nipple having a pitch and taper as set forth. In a more general sense, the number of degrees backed-off will depend on the pitch and taper of the nipple-because the clearance between the threads is a function of these two variables. For standard nipples having a one-third pitch and a taper of l to 6, the number of degrees backed off will typically be a value from about 45 to about 90; for standard nipples having a one-fourth pitch (4 threads per inch and a taper of l to 6, the number of degrees backed off will typically be a value from about 60 to about l35). v I

In the embodiment of FIG. 2, such-a centering'jig is illustrated, and is employed in order to pre-position the nipple in the electrode socket and in order to provide a clearance at the idle flank of the threads of the nipple and the internal threads of the electrode section into which the nipple is threaded.

The centering jig consists of an internally threaded plate 18 which is threaded onto one end of the nipple IQCasters 19 are coupled through holes in the centering plate to l inches diameter bore air cylinders 17. Three casters and three air cylinders are typically used, the casters being so spaced as to form an equilateral triangle against the face 4 of the electrode section 2. A source of air (not shown) provides air under pressure to air cylinders 17. The arrangement is such that the casters l9 push in one direction against the face of the electrode section while the threaded plate 18 pulls the nipple l in the opposite direction, thus applying an axial pressure or force upon the nipple and prepositioning the nipple in'the socket of theelectrode section, and thus providing a clearance between the non-load bearing or idle flanks 13 of the threads of the nipple and the threads of the electrode section. (Axial,

or lengthwise" and transverse or crosswise" directions are shown in FIG. 1).

The following discussion of the makingof a nippleelectrode section pre-assembly further describes the arrangement of FIG. 2.

6 The electrode section'and nipple were the samesize as were employed in the discussion of FIG. 1, as was the diameter of the longitudinal hole 8. The nipple l was hand-tightened into the socket of the electrode section 2, (i.e. the. threads of both the nipple and the socket were completely engaged). The aforedescribed centering jig was then connected to the assembly by threading plate 18, which was 2 inches thick, onto the free end of the nipple. The centering jig device was then turned on by pressurizing the air cylinders 17 to 200 psieach. (Casters 19 were in contact with the face 4 of theelectrode section 2). By doing this an axial force was exerted upon the nipple in a direction away from the electrode section. While this axial force was still being applied, the nipple was backed off 45 thus providing a clearance between the idle flanks 13 of the threads of the nipple and thejopposing flanks of the threads of the socket of the electrode section 2 and thus pre-positioning the nipple in the socket of the electrode section. This axial pressure also caused the loadbearing flanks ll of the threads of the nipple (viz. the flanksnearer the geometric center of the nipple) to remain in direct and close contact with the mating threads of the electrode socket. Coal tar pitch, having a melting point of C, was heated to 200C .and a measured amount of this hot molten fluid was injected through the longitudinal hole 8 and into the cavity or space 5 between the base 6 of the nipple and the base or bottom 7 of the electrode section socket. A sufficient amount of the pitch was employed so as to, immediately upon introduction without undergoing any subsequent expansion, substantially fill the space 5 and extend well up into the longitudinal bore 8, such as to a heightas illustrated in FIG. 1. The nipple-electrode section pre-assembly was maintained in a fixed position until the molten'pitch material had cooled to substantially ambient temperature, thereby causing the pitch to become substantially solid, after which the pressure was released and the jig removed. (A typical cooling time is from 5 to 10 minutes). The pitch solidified at a temperature substantially the same as its melting point. The specific (floating) position of the nipple in the electrode section socket, previously provided by the centering jig, was maintained by the solidification of the pitch which alsotightly fixed the nipple in the electrode section socket. The pre-assembly was thus in the desired condition for subsequent employment in an electrode joint by coupling the pre -assembly to a sec- 3 0nd electrode section. a

An obvious danger of shipping an electrode-nipple pre-assembly is the possibility of damage while in transit. This can be overcome in the present invention by protecting the entire exposed machined threaded portion and end or face of the nipple (and typically also,

the electrode section face as well) with a suitable covple into the socket of the second electrode sectionuntil I the endfaces of thetwo sections joined by the nipple 7 are in. planar contact. lt will be noted that in the illustrated condition the joint has just been made and the pre-assembly of the electrode section 2 and nipple l are at the top of the joint and the second electrode section 20 to which the pre-assembly is joined is at the bottom of the joint. This relative position of the electrode sections is essential to the success of the joints made according to the present invention. The second electrode section to which the pre-assembly is connected is the upper electrode in the column of electrodes for an electric arc furnace prior to this threading step, after which,

of course, the electrode section of the pre-assembly be comes the upper electrode in the column. The making of the joint and the relative positions, of the electrode sections applies both to on furnace and off furnace assembling techniques. The material in clearance space 5 and hole 8 in this FIG. 4 is still in its solidified condition and has not yet melted.

When the thus assembled joint is then heated up, as it is when it'is used in-an electrode column of a steel furnace, the joint firstreaches a temperature which is sufficiently high so as to melt the pitch and thus cause a downward flowing of a portion thereof from clearance space 5 through hole 8 towar a corresponding clearancespace 5a between the other end of the nipple 1 and the bottom of the socket in electrode section 20. (ln the embodiment ofFIG. 3c the pitch would still flow toward the lower clearance space, even though the exit end of the hole terminates at the surface threads of the nipple rather than at the other end face of the nipple). When the pitch thus melts in this em bodiment mostof it flows into clearance space 5a but some of it also stays in clearance space 5, particularly at the peripheralportions thereof. When the joint is then further heated the pitch in both clearance spaces becomes solid and carbonized, thereby locking the nipple in each of the sockets of the joined electrode sections.

There are severalmaterials which may be used in the present invention to fill the space 5 between the base of the nipple and the base'of the electrode section socket in order to float the nipple in the socket of the electrode section of thepre-assembly andmaintain the nipple in a fixed position in the electrode socket and in order also to be functionable later in locking the electrode sections to the nipple when the pre-assembly is incorporated in an electrode joint and the joint is heated in operation. Pitches and tars are particularly suitable.

In any case the material to be used must be one which is a solid at ambient temperatures (and preferably also up to a temperature of at least about 50C), must be one which will readily melt or flow as a non-gaseous fluid when heated (preferably at relatively low temperatures such as between about 100C and about 150C), (so that it can be readily utilized in preparing the preassembly and also later in preparing the electrode joint), must be one which will resolidify when cooled to ambient temperatures (and preferably by the time it reaches a temperature of about 80C), must be one which is carbonizable (i.e. one that leaves a substantial amount of carbon residue upon heating so that it can perform its locking function in the preparation of the electrode joint when the joint is'heated to a temperature hot enough to re-melt the material and then to carbonize it), and must be one which does not undergo significant expansion, such as of a foaming type, when changing from the liquid to the solid state (so that its volume does not change substantially in going back from the solid to the liquid state when the electrode joint is heated in operation).

The preferred materials contain substantial amounts of pitch, such as all pitch, or pitch-carbon flour combinations, or pitch mixed with minor amounts of carbon aggregate and plasticizer, for example, a mixture comprised of at least about 50 parts pitch and up to about 50 parts carbon aggregate, preferably flour," the term flour typically designating a material having a particle sizing such that all of it would pass through a 20 mesh Tyler screen, a maximum of l'percent be retained on a 35 mesh screen, and 50 to percent of it would pass through a 200 mesh screen. The pitch may be either coal tar pitch or petroleum pitch. "Carbon aggregate is intended to include such materials as finely ground graphite particles (preferred) finely ground calcined or raw petroleum coke particles, finely ground coal particlesand mixtures, the carbon aggregate preferably also all being minus 10 Tyler mesh.

The material may also include a minor percentage of plasticizer, such as up to about 5 percent by weight of the carbonizable material or pitch, in order to produce a less brittle pre-assembly. Typical materials that might be used as plasticizers or plasticicizing agents include stearic acid, kerosene, tars and pitches of lower melting point, etc.

When an electrode section-nipple pre-assembly as described herein is added to a second electrode section of an electric arc furnace column or train, the, nipple in the resulting 3-membered joint (viz. twov electrode sections with the nipple half-threaded into each) will be so located that there will be a substantially even distribution of clearance between the idle flanks of the threads of both halves of the nipple in the electrode section sockets of the final joint assembly, rather than the common and objectionable condition typically encountered in the prior art of no clearance at the idle flank of the threads of the nipple-half assembled first and maximum clearance at the idle flank of the threads of 'the second nipple-half assembled. Consequently, there is a reduction in the thermal stresses between the nipple and the electrode sections into which it is threaded with the result that there is a reduction in the degree of splitting and breakage of the joint in furnace operation.

The net effect, therefore, of centering or balancing the nipple in the joint, is that there are fewer mechanical breakdowns or failures in the operation of the furnace. There are also other advantages inherent in making the nipple-electrode section pre-assemblies and joints in accordance with the present invention. For example, the incidence'of thread stripping from the sockets of the threaded electrode sections is virtually precluded because of the more uniform thread loading attending the centering of the nipple. Also, the same material that is used in the preparation of the pre-assembly acts to lock the joint in a tight position upon its use in the furnace thus further acting to prevent unwinding of the electrode joint and thus carrying out two distinct functions which in prior art practices were only capable of being performed by two separate and distinct solutions for the two problems of: (a) nipple balancing; and

(b) nipple fixing in the sockets of the electrode sec-.

tions.

As has been indicated in connection with F lG. 3d, the possible use of one or more holes in the nipple, in addition to the lengthwise hole illustrated in the drawings, is also within the scope of the invention. Such hole or holes may, for example, be within the nipple in one or both ends thereof and connect at an angle or intersect the hole which extends lengthwise in the nipple; or such hole or holes may take the form of a slot or slots atthe surface of the nipple and extend in the lengthwise direction of the nipple from point(s) short of the major diameter and extending to one end of the nipple so as to connect with or communicate with the clearance space between the base of the nipple and the bottom of the electrode section socket. Such additional hole or holes or slot(s) may sometimes be desirably resorted to in order to increase the strength of the connection between the nipple and the electrode section(s) to which it is joined, particularly in cases where the requirement to disengage the nipple from either or both of the electrode sections to which it has been joined is not likely to occur.

An additional advantage of the present invention is that if for any reason it is desired to unthread one of the electrode sections from the nipple (after carbonization) this may readily or controllably be accomplished with certain of the embodiments by using untorquing pressures of the same order or at levels slightly higher than the joint assembly torque level. This is not possible with many joints of the prior art without causing mechanical damage or destruction of one or more of the joined members.

It is to be understood that the invention is not limited to the specific details which havebeen offered merely for illustrative purposes and that modifications may be made within the scope of the appended claims without departing from the'spirit of the invention.

I claim:

1. An electrode section-nipple assembly comprising:

a. a cylindrical electrode section containing internally threaded sockets extending into the section from each of its end faces;

b. a threaded nipple, having at least one lengthwise hole therein which starts at a point in an end face of one-half of the nipple and which terminates at a point in the surface of the other half of the nipple, threaded into and pre-positioned in one of the sockets of said electrode section with the load bearing flanks of the nipple threads, which are the flanks nearer to the geometric center than to the ends of the nipple, in contact with themating faces of the threads of the electrode section socket and with a space between the base of the nipple and the bottom of the electrode section socket; and

c. a solidified carbonizable spacing material situated within the lengthwise hole of the nipple and the space between the base of the nipple and the bottom of the socket of the electrode section, said material having been introduced as a hot, fluid material at the opposite end of the hole in the nipple after the pre-positioning of said nipple; and said material having cooled and solidified to thus maintain the aforesaid pre-positioning of the nipple, thereby securing the nipple in the electrode section socket, and thus also maintaining a clearance between the non-load bearing flanks of the nipple threads and said threaded electrode socket.

2. An assembly according to claim 1 wherein the hole extends lengthwise from one end face of the nipple to the other end face.

3. An assembly according to claim 1 wherein the solidified carbonizable material includes a substantial amount of pitch.

4. An assembly according to claim 1 wherein the solidified carbonizable material consists of pitch mixed with minor amounts of plasticizer and carbon aggre- 

2. An assembly according to claim 1 wherein the hole extends lengthwise from one end face of the nipple to the other end face.
 3. An assembly according to claim 1 wherein the solidified carbonizable material includes a substantial amount of pitch.
 4. An assembly according to claim 1 wherein the solidified carbonizable material consists of pitch mixed with minor amounts of plasticizer and carbon aggregate. 